This invention relates to lasers and more particularly to a compact pulsed gas transport laser.
There is need for a source of coherent light at the 2-to 4-micrometer band which is capable of producing 5 watts or more of pulsed average output power continuously for several hours and is sufficiently compact (about 10 ft..sup.3) and light weight to be practicable for airborne use. Such a laser is useful for optical countermeasures and reconnaissance. No known laser head is available which meets these requirements. A laser head is defined as that part of the laser system including and within the vacuum enclosure (including the heat exchanger, discharge electrodes, optical path, gas flow system), the optical cavity system (including the mirror, windows, and optical bench), and the integral pulse forming network.
One type of prior compact, lightweight laser head is a scaled-down version of the carbon dioxide laser described in U.S. Pat. No. 3,772,610 and in an article entitled "Performance of a Compact Sealed 200-W CO.sub.2 Laser" by T. S. Fahlen, IEEE J. Quantum Electron. (corresp.) Vol. QEll, pp. 848-849, October 1975. In this system, the gas is rapidly recirculated through the laser electrode discharge gap and heat exchanger by means of a vane axial blower and motor located within the laser housing. While this system is comparatively compact and lightweight, it is incapable of meeting the ultra-high vacuum (10.sup.-5 Torr) and gas purity requirements needed to achieve long life and efficient operation because, inter alia, of outgassing of the blower motor.
Another prior system is described in "Closed-Cycle Rare-Gas Electrical Discharge Laser", Final Report AFAL-TR-77-13 (1977), by R. Olson and D. Grosjean and utilizes a vane axial fan within a vacuum tight shell driven by a motor outside the shell. While this system maintained high vacuum integrity, it was approximately ten feet long and is believed to weigh several hundred pounds. This is clearly impracticable for space limited applications including airborne uses.